Handheld sampling head, analysis setup and method for characterizing an aerosol

Abstract

Handheld sampling head (1) for taking a sample of an aerosol containing airborne particles, with a sampling line (2) and with an integrated dilution unit (3) which is connected to the sampling line (2) and which has a dilution air inlet (4), characterized in that the dilution unit (3) has a first element (6) with a first contact surface (7) and a second element (8) with a second contact surface (9), which are arranged to be movable relative to each other and which are in planar contact with each other with their respective contact surfaces (7, 9), that in the first element (6) a sample channel (10) open towards the second element (8) is formed in the first contact surface (7), which is connected to the sampling line (2), that in the first element (6) a dilution air channel (11) open towards the second element (8) is formed in the first contact surface (7),which is connected to the dilution air inlet (4), that in the second element (8) in the second contact surface (9) at least one receiving space (14) open towards the first element (6) is formed such that the receiving space (14) can be brought into contact with the sample channel (10) and with the dilution air channel (11) successively during the relative movement (28) of the first element (6) against the second element (8), and that the first element (6) and the second element (8) are made of ceramic.

Description

The invention relates to a handheld sampling head for taking a sample of an aerosol containing airborne particles, with a sampling line and with an integrated dilution unit which is connected to the sampling line and which has a dilution air inlet. Such sampling heads are known in analytical setups for the analysis or characterization of aerosols, where the sampling head serves to extract a sample volume from a larger sample reservoir or flowing aerosol. In this process, dilution air or a dilution gas is often added to the extracted sample volume in the dilution unit to enable or facilitate subsequent analysis. EP 2 264 423 A2, for example, describes a device comprising a pre-diluter, a downstream heated evaporator, a secondary diluter downstream of the evaporator, and a particle counter connected thereto. The secondary diluter is designed as a porous tube diluter and is arranged between the evaporator outlet and a stabilization chamber from which the sample stream for the particle counter is diverted. This allows the concentration of solid particles to be measured in a simple and widely controllable manner without interference from volatile aerosol particles. Furthermore, AT 009 603 U2 discloses a rotary diluter comprising a rotatable rotating element which carries surface-accessible transfer volumes that alternately pass over inlet and outlet openings for an undiluted fluid flow on the one hand and a dilution fluid flow on the other along their common path of movement. To easily extend the usable dilution rate range, the rotating element has at least two rows of transfer volumes on different paths of movement, the associated inlet openings of which for the undiluted fluid flow and / or the dilution fluid flow can be controlled separately. Furthermore, US 2010 / 0284006A1 describes a system comprising an inertial filter, a temperature controller, and an analyzer. The inertial filter has several ports, including a first port, a second port, and a third port. A sample gas flows between the first and third ports of the inertial filter. The second port of the inertial filter discharges a portion of the gas flowing between the first and second ports. The temperature controller regulates the temperature of the inertial filter and / or the gas flowing through it. The analyzer receives the portion of the gas flow discharged from the second port of the inertial filter and generates a value indicating the concentration of sulfur trioxide in that portion of the gas flow. The invention therefore further relates to an analysis arrangement for characterizing an aerosol. Finally, the invention relates to a method for characterizing an aerosol, wherein the aerosol comprises a carrier gas and suspended particles contained therein, a sample stream containing the aerosol and a dilution air stream are supplied to a dilution unit, a predetermined volume of the sample stream and the dilution air stream are exchanged against each other in the dilution unit, and downstream of the dilution unit, the dilution air stream is supplied to a particle determination unit with which a number and / or mass fractions of the suspended particles can be determined. The amendment to the First Federal Immission Control Ordinance requires a reduction in the limit value for dust and particle emissions from small and medium-sized solid fuel plants. The invention is based on the objective of creating an easy-to-use measuring device that is suitable for a wide range of applications. To solve this problem, the invention provides, in a handheld sampling head of the type mentioned above, that the dilution unit comprises a first element with a first contact surface and a second element with a second contact surface, which are arranged to be movable relative to each other and which make planar contact with each other with their respective contact surfaces, that in the first element a sample channel open towards the second element is formed in the first contact surface and which is connected to the sample line, that in the first element a dilution air channel open towards the second element is formed in the first contact surface and which is connected to the dilution air inlet, and that in the second element at least one receiving chamber open towards the first element is formed in the second contact surface.that the recording space can be successively connected to the sample channel and the dilution air channel during the relative movement of the first element against the second element. The invention thus provides a handheld sampling head with a dilution principle that differs from the known valve technology, with which high dilution factors can be achieved without requiring an excessively large dilution airflow. The invention offers the possibility of achieving these high dilution factors by not adding the dilution air to the sample volume, as with known valve techniques, but rather by adding parts of the sample volume to the dilution air. Since the dilution principle implemented in the sampling head according to the invention does not require valves, the sample volume does not need to be passed through a valve, which would result in a relatively rapid clogging of the valve in question. To save space in the sampling head, the dilution unit can be arranged in a disc shape, with the first and / or second element being / are disc-shaped. The contact surfaces can then be located on a side of the disc shape. To realize the dilution principle, different relative movements between the elements are possible, by which at least one receiving chamber between the sample channel and the dilution air channel is moved back and forth. Relative movements without a reversal point are particularly advantageous from a mechanical point of view. For example, it may be provided that the first element and the second element are arranged to rotate relative to each other about an axis of rotation. Thus, at least one recording space between the sample channel and the dilution air channel can be repeatedly moved back and forth. It is possible to arrange the first element in a stationary position. This allows for the simple supply of the sample volume via the sample line into the sample channel and the supply of the dilution air via the dilution air inlet into the dilution air channel. To achieve the relative motion, it can be provided that the second element is rotatably mounted. To optimally utilize the openings provided by the sample channel and the dilution air channel, and to achieve good mixing between the at least one sampling chamber and the sample channel or the dilution air channel, the sample channel and / or the dilution air channel can be designed in a kidney shape along a circular arc. It is advantageous that the at least one sampling chamber can be guided along the entire longitudinal extent of the sample or dilution air channel during relative movement. To automatically execute the relative movement, the second element can be arranged in a rotationally fixed manner on a preferably motor-driven shaft. Particularly good space utilization and particularly good accessibility of the second element can be achieved if the wave passes through the first element. It can be arranged that the shaft is driven on the side of the first element facing away from the second element. An advantage of this is that the second element can be easily placed on or removed from the shaft for maintenance purposes without having to disconnect the drive connection of the driven shaft. To ensure easy access to the dilution unit for maintenance purposes and the like, it may be provided that the dilution unit is arranged under a cover cap, the cover cap being connected to the rest of the sampling head housing. For example, the cover cap can be detachably attached to the housing. A seal can be formed at the connection point. It is particularly advantageous if the cover cap is attached to the housing with a screw or bayonet fitting. To easily achieve full-surface contact between the first and second elements, a resilient element can be provided to axially actuate the second element. This resilient element can be, for example, a spring, an elastically deformable solid body, or the like. The spring element can be designed to rest against the cover cap. This has the advantage of allowing for easy assembly of the dilution unit. The surface contact of the first element with the second element at the respective contact surfaces can be gas-tight to prevent the escape of gases / aerosols from the sample channel or the dilution air channel or the at least one receiving chamber. To prevent wear on the contact surfaces, the first and second elements can be made of identical material. It is advantageous if both elements have the same degree of hardness, thus minimizing wear. According to the invention, the first element and the second element are made of ceramic. This results in a particularly stable dilution unit. To avoid unwanted, aggressive condensation in the dilution unit, a heating device for heating the dilution unit may be integrated. It is particularly advantageous if the heating device is set up to heat the first element and / or the second element. For example, this can be achieved by using a heating film in the heating device that lies flat against the first or second element. The advantage here is that a heating film requires little installation space and that the flat contact allows for good heat transfer to the heated element. For example, the heating film can be positioned on the side of the first element facing away from the second element. This allows the heating film to be located away from moving parts and protected from mechanical damage. To improve the utilization of the heating power of the heating device, it may be provided that the first element and / or the second element is / are enclosed by a heat-insulating encapsulation. To prevent unwanted, aggressive condensation and to avoid falsifying measurement results, the sampling line may be equipped with a heater. Preferably, the heater extends over the entire or substantially the entire length of the sampling line. In one embodiment of the invention, the dilution air duct can be connected downstream of the dilution unit to a measuring hose made of electrically conductive material. For example, the measuring hose can be made of a chemically resistant, conductive hose, preferably silicone with carbon enrichment. An advantage of this is that electrostatic charging of the measuring hose by suspended particles contained in the conveyed air is avoided. Such electrostatic charging would lead to the removal of the suspended particles from the dilution air, which is enriched with these particles for further measurements. This would result in a distortion of the measurement result. A counting device can be provided for the receiving chambers that are moved back and forth between the sample channel and the dilution air channel per unit of time. An advantage of this is that the volume transported and exchanged by the receiving chamber(s) per unit of time can be easily determined, for example, by measuring the rotational speed of a relative movement. The counting device can be integrated into the sample collection head or the analyzer of an analytical arrangement according to the invention. Therefore, if the speed of the driving motor is regulated, the number of sampling chambers that transported a volume of sample from the sample side to the dilution air side per unit of time can be determined with very low error. Multiplying the number of sampling chambers by their volume yields the total volume of sample transported. Since the suspended particles detected in a downstream particle analysis unit can only originate from the sample stream, the dilution air flow can vary within a certain range and does not need to be precisely controlled. Consequently, the volumetric flow rates through the dilution unit do not need to be strictly constant, which significantly reduces the demands placed on downstream pumps and the flow resistance of the pipes. To achieve particularly precisely defined dilution ratios, the dilution air inlet and the sampling line can be connected at one or more ends of the dilution air duct, and the sampling line at the other end of the sampling channel, in such a way that the flow directions are aligned with respect to the relative movement of the first element relative to the second element. It is advantageous that the longest possible contact time between the at least one receiving chamber and the respective channel is achieved during the relative movement. Therefore, during the relative movement, the at least one receiving chamber first comes into contact with the end of the dilution air duct where the dilution air inlet opens, and first with the end of the sampling channel where the sampling line opens. It can also be provided that the relative movement of the first element against the second element is arranged such that the at least one receiving chamber is guided along the dilution air duct against its flow direction. An advantage of this is that good mixing between the volume contained in the receiving chamber and the volume contained in the dilution air duct can be achieved through turbulence even at slow flow velocities. To solve the problem, the invention provides, in the analysis arrangement described above, that a sample collection head according to the invention is connected to a portable analysis device. The advantage here is that a measuring device is provided which is suitable for many areas of application, for example for monitoring the transport and production of substances / products containing high levels of particles, for general combustion plants and the like. To limit the number of individually handled parts of the analysis setup, a dilution air filter can be integrated into the analyzer and connected to the dilution air inlet of the sampling head. It is also advantageous to position the intake port of the dilution air filter as far away as possible from the sampling head, thus largely preventing any uncontrolled release of sample contents into the dilution air. To determine the mass of suspended particles in the aerosol, the analyzer can be provided with an impactor connected to the dilution air channel of the dilution unit. An advantage of this is that the particularly high dilution factor achievable with the dilution unit according to the invention is well suited for the impactor measurement method. In one embodiment of the invention, the analytical instrument may include at least one sensor for determining at least one gaseous component in the carrier gas of the aerosol, which is connected to the sample channel of the dilution unit. An advantage of this is that the sample volume exiting the dilution unit practically or at least approximately undiluted can be used for component analysis. The resulting re-dilution can be easily corrected computationally. The analysis arrangement according to the invention is thus able to measure the gas concentration (for example O2 and CO or other components) in parallel, i.e. simultaneously or at close intervals, in addition to determining the mass and / or number of suspended particles (particle concentration and / or particle number in a particle size range) at the impactor. To ensure compliance with the sensor's measuring ranges, an additional dilution unit may be installed upstream of the sensor. This additional dilution unit is thus located downstream of the first dilution unit and preferably operates according to a different dilution principle, for example, using nozzle or valve technology. The dilution unit is preferably integrated into the analyzer. For the operation of the impactor, the analyzer may be equipped with a pump positioned downstream of the impactor in the suction direction. An advantage of this configuration is that the pump cannot distort the impactor's measurement results. It is also possible for the analyzer to include a pump positioned upstream of at least one sensor in the suction direction. An advantage of this design is that the sensor can operate without pressure. The subsequent gas path can therefore be open to an exhaust after the sensor. Preferably, separate pumps are designed for the impactor and the sensor in order to optimally meet the respective requirements. To solve the problem in the aforementioned method, the invention provides that, downstream of the dilution unit, the sample stream is fed to at least one sensor for determining at least one gaseous component in the carrier gas of the aerosol. The particle determination unit can be designed as a mass determination unit, which is configured to determine the mass fractions of the suspended particles. Thus, it is possible to simultaneously determine both the mass fractions of the suspended particles – for which a high dilution factor is required – and the components of the carrier gas – for which a different dilution factor is required. The exchange according to the invention results in two streams after dilution that can be used separately for different tasks, whereas with the previously known valve technology, only one stream is available after dilution, which can be used either for determining mass fractions or for determining gaseous components. The determination of the gaseous components can, for example, include determining the type of components and / or determining the proportions of the components in the carrier gas. For easy evaluation of the measurement results, the invention provides that a volume quantity is exchanged in the dilution unit per unit of time, thereby establishing a predetermined dilution ratio in the dilution air stream. If the exchange is achieved by a uniform relative movement, for example a uniform circular movement, between a first element containing a dilution air channel and a second element containing at least one receiving chamber, the specified dilution ratio can be easily set by generating the dilution air flow with a constant volume flow. To avoid unwanted, aggressive condensations and contamination, it may be necessary to heat the sample stream before the dilution unit and / or to heat the dilution unit itself. To ensure a constant volume flow and / or to compensate for pressure fluctuations, the dilution air flow may be supplied to a pump via a buffer volume followed by a capillary after the particle determination unit. To monitor the functionality of the particle analysis unit and / or to control the pump output, it may be possible to measure a pressure drop in the dilution air stream above the particle analysis unit and / or the volume flow rate of the dilution air stream. An advantage of this is that a change in the dilution air flow, which could be caused, for example, by a clogged nozzle of an impactor in the particle analysis unit, can be easily detected and displayed. It can be arranged that the volume is exchanged by alternately connecting at least one receiving chamber to the sample stream and the dilution air stream. An advantage of this is that the exchanged volume can be easily predetermined by the size of the at least one receiving chamber. According to the invention, the volume exchanged per unit of time is measured. This is achieved, in particular, by counting how often the at least one receiving chamber is moved back and forth between the sample stream and the dilution air stream per unit of time. If the at least one receiving chamber is moved between the dilution air stream and the sample stream by a rotary motion, the counting can be carried out by measuring or presetting the rotational speed. By measuring the exchanged volume, the number of suspended particles contained in the dilution air is known, so that the measurement results of the particle determination unit are easily evaluated and comparable. For example, it may be possible to calculate the measured volume by combining it with at least one measurement result from the particle determination unit. An advantage of this approach is that it allows for a simple standardization of the particle determination unit's measurement results, which may even be legally required. The invention will now be described with reference to an exemplary embodiment, but is not limited to this embodiment. Further exemplary embodiments result from combining one or more features of the claims with each other and / or with one or more features of the exemplary embodiment. It shows: Fig. 1: a three-dimensional sectional view of a sampling head according to the invention, Fig. 2: the dilution unit of the sampling head according to Fig. 1 in a partial exploded view, Fig. 3: the sampling head according to the invention according to Fig. 1 in a three-dimensional sectional view from a further angle, Fig. 4: the dilution unit of the sampling head according to Fig. 1 in a three-dimensional sectional view from a further angle, Fig. 5: a first element of the dilution unit according to the invention according to Fig. 2 in a view of the contact surface, Fig. 6: the first element according to Fig. 5 in a view from the opposite side, Fig. 7: the second element of the dilution unit according to the invention according to Fig. 2 in a view of the contact surface, Fig. 8: the second element according to Fig. 7 in a view of the opposite side, Fig.9 : a further three-dimensional sectional view of the sampling head according to Fig. 1 , and Fig. 10 : the gas path diagram of an analysis arrangement according to the invention. Figs. 1, 2, 3, 4, 5, 6, 7, 8 to 9 show different views or components of a sampling head designated as a whole by 1 and are therefore described together below. The sampling head 1 has a sampling line 2, through which an aerosol containing suspended particles is fed to a dilution unit 3. The dilution unit 3 also has a dilution air inlet 4, through which dilution air is supplied to the dilution unit 3 from a dilution air hose 5. The dilution unit 3 has a first element 6, which is disc-shaped and provides a first contact surface 7. The dilution unit 3 further has a second element 8, which is also disc-shaped and has a matching basic shape to the first element 6. The second element 8 provides a second contact surface 9, which in the operating position lies flat and gas-tight on the first contact surface 7. As can be seen particularly well from the detailed illustrations according to Fig. 5 and Fig. 6, a sample channel 10 is formed in the first contact surface 7 of the first element 6, which is open to the second element 8 in the operating position. In the first contact surface 7, a dilution air channel 11 is further formed, which is also open towards the second element 8 in the operating position. The sample channel 10 and the dilution air channel 11 each extend in a kidney shape along a circular arc. These circular arcs have a matching radius and a matching center, which coincides with the center of rotation of the second element 8. The sample channel 10 is connected at one end 12 to the sample extraction line 2, while the dilution air channel 11 is connected at one end 13 to the dilution air inlet 4. In the second contact surface 9 of the second element 8, ten receiving spaces 14 are provided as cavities. The recording rooms 14 are arranged on a circle around the center point of the second element 8, which is also the pivot point of the second element 8. In other embodiments, different numbers of recording rooms 14 are implemented, for example a single recording room, two, three or more than three recording rooms 14. The receiving chambers 14 in the embodiment according to Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5, Fig. 6, Fig. 7, Fig. 8 to Fig. 9 are arranged with respect to the center of rotation of the second element 8 such that when the second element 8 is rotated against the first element 6 in the operating position, the receiving chambers 14 are alternately connected to the sample channel 10 and the dilution air channel 11 one after the other. This allows for a gas or aerosol exchange between the contents of the receiving chamber 14 on the one hand and the sample channel 10 or the dilution air channel 11 on the other, thereby effecting an exchange of a volume quantity determined by the size of the receiving chambers 14 between a sample stream flowing in the sample channel 10 and a dilution air stream flowing in the dilution air channel 11. This ensures that dilution can be carried out without increasing the pressure on one side. In the relative movement of the second element 8 with respect to the first element 6, which in the illustrated embodiment is a rotary movement or uniform circular movement, the first element 6 remains stationary, while the second element 8 is connected to a shaft 15 in a rotationally fixed manner, which is driven by a motor 16. For this purpose, the wave 15 is guided through a central opening 17 of the first element 6 and extends through it. Drivers 18 are formed on the shaft 15, which extend in a radial direction and which engage in suitable recesses 19 on the second element 8 for a rotationally fixed connection of the second element 8 which is mounted on the shaft 15. The first element 8 is attached to the sampling head by means of fasteners which are inserted into four mounting holes 50. A conical step 20 provides a functional connection between the driven shaft 15 and the electric motor 16, whereby the electric motor 16 can be arranged with its longitudinal axis aligned in the extension direction of the handle 21. The dilution unit 3 is arranged under a removable cover cap 22. The cover cap 22 is hood-shaped and connected to the rest of the housing 23. A spring 24 (or other spring element) is inserted between the second element 8 and the cover cap 22, which axially acts on the second element 8 and thus presses the first contact surface 7 and the second contact surface 9 together to form a gas-tight seal. The first element 6 and the second element 8 are made of ceramic material, for example cast, pressed, sintered and / or milled. A heating film 25 is laid flat against the back side 51 of the first element 6, opposite the first contact surface 7 and thus facing away from the second element 8, which, together with the associated electrical circuitry (not shown further), forms a heating device for heating the dilution unit 3. The first element 6, which is thus heated, is enclosed in a shell-shaped encapsulation 26, which insulates the handle 21 and the housing 23 from the heat generated by the heating film 25. A heater 27 is provided along the sampling line 2, with which the sampling line 2 can be kept above the condensation temperature of the aerosol. The heating film 25 is also operated at a temperature which prevents condensation in the dilution unit 3. As can be seen in more detail in Fig. 5, the opening of the sampling line 2 and the dilution air inlet 4 are arranged at the ends 12, 13 of the sampling channel 10 and the dilution air channel 11 respectively, such that with respect to the relative movement 28, i.e. the rotation of the second element 8 against the first element 6, flow directions 29, 30 are defined that are in the same direction to each other. In the exemplary embodiment, the flow directions 29, 30 both have the opposite direction of rotation to the relative movement 28. The drawn relative motion 28 denotes the motion of the second element 8 relative to the stationary first element 6. Thus, the receiving chambers 14 are guided along the dilution air duct 11 in its flow direction 30. The sampling head 1 shown in Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5, Fig. 6, Fig. 7, Fig. 8 to Fig. 9 is used in an analysis arrangement 31, the gas path diagram of which is shown in Fig. 10. It is evident that the sampling head 1 is connected to an analyzer, which is formed by the details shown in Fig. 10 next to the dilution unit 3 and the sampling line 2. The analyzer of the analysis arrangement 31 therefore has a particle determination unit 32 with an impactor 33, which is connected to the dilution air duct 11 via a measuring hose 34, cf. Fig. 1 , Fig. 2 , Fig. 3 , Fig. 4 to Fig. 5 . The measuring hose 34 is made of silicone with carbon enrichment, which forms an electrically conductive material. The particle determination unit 32 can be used to determine the mass fractions of the suspended particles in the aerosol. The analyzer of the analysis arrangement 31 further has an integrated gas analyzer which has one or more sensors for determining at least one gaseous component in the carrier gas of the aerosol. The gas analyzer 35 is preceded by a combination device 37, comprising a condensate trap and a fine filter, and a particle filter 39, which are connected to the outlet of the sample channel 10 via a sample line 40. The dilution air hose 5, measuring hose 34 and sample line 40 as well as electrical connecting lines 41 are led to the analyzer in a sheath which is not shown further. The gas analyzer 35 is equipped with a pump (not shown) which generates a sample flow in the sample channel 10. Downstream of the impactor 33 is a further pump 42, with which a dilution air flow can be generated in the dilution air duct 11. To generate a uniform dilution air flow, the pump 42 is provided with a combination of a buffer volume 43 and a capillary 44 downstream of it. The capillary 44 is operated supercritically, so that an increase in pump pressure does not result in a significant change in the delivery volume. To protect the capillary 44, a filter 45 is arranged between buffer volume 43 and capillary 44. In another embodiment, the capillary 44 and the filter 45 are not present. The rotational speed of the motor 16 (see Fig. 1) is controlled in the sampling head 1. A counting unit, not shown in further detail, is integrated into the sampling head 1 or the analyzer (in particular the particle determination unit 32) of the analysis setup 31. This counting unit derives the number of receiving chambers 14 moving back and forth between the sample channel 10 and the dilution air channel 11 by the rotation from the actual rotational speed, with each receiving chamber 14 moving back and forth multiple times being counted multiple times. Knowing the volume of a receiving chamber 14, the quantity of sample added to the dilution air can then be calculated. The measurement result at the particle determination unit can thus be normalized to this volume and / or a standard volume. The impactor 33 of the embodiment according to Fig. 10 can be monitored by pressure sensors 46, 47, with which the pressure difference or pressure drop across the impactor 33 can be measured. The pumping capacity of the pump 42 is controlled based on the measured pressure difference across the impactor 33. The dilution airflow can be monitored with a dV / dt sensor 48, with which a volume flow of the dilution airflow can be measured. With the buffer volume 43 and the capillary 44, a constant volume flow for the dilution air flow can be set, which can be monitored with the pressure sensors 46, 47 and / or with the dV / dt sensor 48. Furthermore, a filter 49 for cleaning the dilution air drawn in via the dilution air hose 5 is arranged in the analysis device of the analysis arrangement 31. In the sampling head 1 of an analysis arrangement 31, it is provided that in a dilution unit 3 a sample stream supplied via a sampling line 2 and a dilution air stream supplied via a dilution air inlet 4 are mixed in such a way that a volume quantity carried in at least one receiving chamber moved with a movable element 8 is exchanged between the sample stream and the dilution air stream, wherein the analysis arrangement 31 has a gas analyzer 35 for analyzing the slightly diluted sample stream and a particle determination unit 32 for analyzing the enriched dilution air stream.

Claims

Handheld sampling head (1) for taking a sample of an aerosol containing airborne particles, with a sampling line (2) and with an integrated dilution unit (3) which is connected to the sampling line (2) and which has a dilution air inlet (4), characterized in that the dilution unit (3) has a first element (6) with a first contact surface (7) and a second element (8) with a second contact surface (9), which are arranged to be movable relative to each other and which are in planar contact with each other with their respective contact surfaces (7, 9), that in the first element (6) a sample channel (10) open towards the second element (8) is formed in the first contact surface (7), which is connected to the sampling line (2), that in the first element (6) a dilution air channel (11) open towards the second element (8) is formed in the first contact surface (7),which is connected to the dilution air inlet (4), that in the second element (8) in the second contact surface (9) at least one receiving space (14) open towards the first element (6) is formed such that the receiving space (14) can be brought into contact with the sample channel (10) and with the dilution air channel (11) successively during the relative movement (28) of the first element (6) against the second element (8), and that the first element (6) and the second element (8) are made of ceramic. Sample collection head (1) according to claim 1, characterized in that the first element (6) and / or the second element (8) is / are disk-shaped and / or that the first element (6) and the second element (8) are arranged rotatably relative to each other about an axis of rotation and / or that the first contact surface (7) is gas-tight against the second contact surface (9). Sample collection head (1) according to claim 1 or 2, characterized in that the first element (6) is arranged in a stationary position and / or that the second element (8) is rotatably mounted and / or that the sample channel (10) and / or the dilution air channel (11) is / are kidney-shaped along a circular arc. Sample collection head (1) according to one of claims 1 to 3, characterized in that the second element (8) is arranged non-rotatably on a driven shaft (15) and / or that the shaft (15) passes through the first element (6) and / or that the shaft (15) is driven on the side of the first element (6) facing away from the second element (8). Sample collection head (1) according to one of claims 1 to 4, characterized in that the dilution unit (3) is arranged under a cover cap (22), wherein the cover cap (22) is preferably detachably connected to a further housing (23) of the sample collection head (1), and / or that a resilient element, in particular a spring (24), axially acts on the second element (8), in particular wherein the resilient element (24) is supported on the cover cap (22). Sample collection head (1) according to one of claims 1 to 5, characterized in that a heating device (25) for heating the dilution unit (3), in particular the first element (6) and / or the second element (8), is integrated and / or that the heating device has a heating film (25) which lies flat against the first element (6) or the second element (8), and / or that the heating film (25) is arranged on the side of the first element (6) facing away from the second element (8). Sample collection head (1) according to one of claims 1 to 6, characterized in that the first element (6) and / or the second element (8) is / are enclosed by a heat-insulating encapsulation (26) and / or that the sample collection line (2) has a heater (27). Sample collection head (1) according to one of claims 1 to 7, characterized in that the dilution air channel (11) is connected in the flow direction (30) behind the dilution unit (3) to a measuring hose (34) made of electrically conductive material, in particular silicone with carbon enrichment. Sample collection head (1) according to one of claims 1 to 8, characterized in that a counting device is provided for receiving chambers (14) that are moved back and forth between the sample channel (10) and the dilution air channel (11) per unit of time. Analysis arrangement (31) for characterizing an aerosol, characterized in that a sampling head (1) according to one of claims 1 to 9 is connected to a portable analysis device. Analysis arrangement (31) according to claim 10, characterized in that a dilution air filter (49) is integrated into the analysis device, which is connected to the dilution air inlet (4) of the sample collection head (1), and / or that the analysis device has an impactor (33) which is connected to the dilution air channel (11) of the dilution unit (3), and / or that the analysis device has at least one sensor (36) for determining at least one gaseous component in the carrier gas of the aerosol, which is connected to the sample channel (10) of the dilution unit (3), and / or that an additional dilution unit is connected upstream of the sensor (36). Analysis arrangement (31) according to claim 10 or 11, characterized in that the analysis device has a pump (42) which is arranged downstream of the impactor (33) in the suction direction, and / or that the analysis device has a pump which is arranged upstream of the at least one sensor (36) in the suction direction. A method for characterizing an aerosol, wherein the aerosol comprises a carrier gas and suspended particles contained therein, a sample stream containing the aerosol and a dilution air stream are supplied to a dilution unit (3), a predetermined volume of the sample stream and the dilution air stream are exchanged in the dilution unit, and downstream of the dilution unit (30) the dilution air stream is supplied to a particle determination unit (32) with which a number and / or mass fractions of the suspended particles can be determined, characterized in that downstream of the dilution unit (3) the sample stream is supplied to at least one sensor (36) for determining at least one gaseous component in the carrier gas of the aerosol, and that a volume is exchanged per unit time in the dilution unit (3).by which a predetermined dilution ratio is established in the dilution air stream, wherein the volume exchanged per unit of time is measured by counting how often per unit of time the at least one receiving chamber (14) was moved back and forth between the sample stream and the dilution stream. Method according to claim 13, characterized in that the dilution airflow is generated with a constant volume flow. Method according to claim 13 or 14, characterized in that the sample stream is heated upstream of the dilution unit (3) and / or that the dilution unit (3) is heated and / or that the dilution air stream is fed downstream of the particle determination unit (32) through a buffer volume (43), followed by a capillary (44), to a pump (42) and / or that a pressure drop in the dilution air stream above the particle determination unit (32) and / or the volume flow rate of the dilution air stream is / are measured. Method according to one of claims 13 to 15, characterized in that the volume quantity is exchanged by alternately connecting at least one receiving chamber (14) with the sample stream and the dilution air stream and / or that the measured volume quantity is offset against at least one measurement result of the particle determination unit (32).

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